ASTR 380Possibilities for Life on Mars

Last Lecture: Venus (this lecture) This Lecture: Mars – Chapter 8

Remember: We have visited the Moon with people.We only have rocks from the Moon to study on Earth!

We are examining the possibilities in these lectures. • Seeing what existing evidence says• What we can infer• Few 100% conclusions

Possibilities for Life in the Inner Solar System

Possibility of Life in the Inner Solar System

The Moon, Mercury, and the Moons of MarsDeimos

Phobos

Moon

Mercury

NO LIFE NOW or EVERThis is a 98% conclusion!

Possibility of Life in the Inner Solar SystemThe Venus versus our checklist:

chemical building blocks: Earth-like origin. Lots of C, N, O.But currently low on water!

energy: reasonable sunlight. Hot temperatures a problemfor Earth type complex molecules

liquid: No. Too hot for water

stability: Very hot and dry now. Surface may have episodes of extreme volcanic activity.

Very poor chance for current life.Small chance of life in the past.

Possibility of Life on Mars

What do we know about Mars?

Rocky surfaceThin amosphere“ice” on polesDust storms

Possibility of Life on Mars

Possibility of Life on Mars

Possibility of Life on MarsMartian atmosphere – about 1% of Earth

Possibility of Life on MarsMartian surface temperature:

Average temperature: 210 K = -63 C

Typical highs: 260 K

Typical lows: 195 K

Highest measured: +5 C

Soil temperaturehigh: +27 C

Possibility of Life on Mars

History of exploration:

US: Mariner 4 flyby in 1964

Russia: Mars 2 and 3 landed on surfacein 1971lost contact within seconds

Mariner 4

Mars image from Mariner 4

Mars 2

Possibility of Life on Mars

History of exploration:

US: Viking 1 and 2 in 1976Composed of orbiter and landerOperated until 1982 and 1980

Possibility of Life on Mars

US: Viking 1 and 2 in 1976

Viking 2

Viking 1 first image

Possibility of Life on Mars

Viking 2

Viking 1: rocks and sand dunes

Possibility of Life on Mars

Viking 2

Viking 1 and 2 had four biological experiments.

Gas Chromatograph and Mass Spectrometer-- searched for organic molecules in soil

Gas Exchange-- incubate soil sample to search for gases created

by biological activity

Possibility of Life on MarsLabeled Release

-- “fertilized” soil with 14C labeled nutrients then looked for 14C in released gases

Pyrolytic Release-- exposed soil to CO and CO2 with 14C labeling, let sit

for several days, then checked soil for 14C componds

Labeled Release

Possibility of Life on Mars

Viking 2

Results:

Gas Chromatograph and Mass Spectrometer-- no organic compounds in soil

Gas Exchange-- no oxygen, CO2, methane released – no bio-activity

Labeled Release-- positive release of 14C containing gases – possible

bio-activity

Pyrolytic Release-- no 14C biomass built-up

Possibility of Life on Mars

Viking 2

Viking Biological Experiment Results:

Most experts now agree that life was not detected byany of the experiments.

It is thought that the Labeled Release experimentdetected chemical reactions with soil – mainevidence is that the activity started high anddecreased with time.

No conclusive evidence for life now active on MarsNo evidence of residual organic molecules

(in these two spots ----within a few inches of the surface)

Possibility of Life on MarsRussia: Phobos 1 and 2 to study moons of Mars (1988)

-- Phobos 1 failed-- Phobos 2 took pictures but lander failed

US: Mars Global Surveyer (1996)-- operated for 10 years taking pictures of Mars from orbit-- 1.6 to 39 ft per pixel, depending on orbital position

Possibility of Life on MarsUS: Mars Global Surveyer (1996 - 2006)

-- see new surface features formed

Possibility of Life on Mars

US: Mars Global Surveyer (1996 – 2006)-- crater forms and fades as

eject become weathered.

Possibility of Life on MarsUS: Mars Global Surveyer (1996 - 2006)

-- Delta feature at 5 ft/pixel resolution

Possibility of Life on MarsUS: Mars Pathfinder – Sojourner (1997)

-- in contact for 83 days-- images-- analysis of rock – high silicon content volcanic rocks-- one rock appeared to be deposited by a flood-- one rock showed clear wind weathering

Possibility of Life on MarsUS: Mars Odyssey (2001 – present)

orbiting optical and thermal imager and Gamma rayspectrometer

Foundhydrogenwhich likelycame fromwater

Possibility of Life on MarsEurope: Mars Express – orbital imager (2004 – present)

Possibility of Life on MarsUS: Mars Rovers – Spirit and Opportunity (2003 – present)

Possibility of Life on MarsUS: Mars Reconaissance Orbiter (2006 – present)-- further detailed imaging of planet in preparation

for a lander exploring the polar cap

Can see 2.3m wide Rover OpportunityUS: Phoenix to land at polar region, analyze ice and look for life -- May 2008

Possibility of Life on MarsWhat is the evidence that there was once water on the

surface of Mars?

Can see 2.3m wide Rover OpportunityRiver-like flow networks

Possibility of Life on MarsWhat is the evidence that there was once water on the

surface of Mars?

Can see 2.3m wide Rover OpportunityRegions that look like river deltas and dried lakebeds

Possibility of Life on MarsWhat is the evidence that there was once liquid water on the

surface of Mars?

Can see 2.3m wide Rover tunityRocks with minerals and microscopic features that likely required water to form.

Oppor

Possibility of Life on MarsWhat is the evidence that there was once liquid water on the

surface of Mars?

Can see 2.3m wide Rover OpportunityThe current polar ice caps are known to contain water ice based on several types of orbital measurements.

By one estimate, the southern ice cap has enough water to cover the entire planet to a depth of 11 meters!!!

Possibility of Life on MarsWhat is the evidence for current or past life on Mars?

Can see 2.3m wide Rover Opportunity

Viking life-detection experiments showed no evidence for currently active life and no evidence for complex organic compounds at two sites – disappointing!

Extensive imaging with around 1 meter resolution finds no evidence for life anywhere on planet.

Any life, current or past would have to be at the cell level.

Possibility of Life on MarsWhat is the evidence for current or past life on Mars?

Can see 2.3m wide Rover Opportunity

Best argument for past life is the ALH84001 meteorite.

-- 4.5 Billion years old rock-- detached from Mars 15 Million years ago in an impact-- landed on Earth 13,000 years ago and found in 1984

Possibility of Life on Mars

Can see 2.3m wide Rover Opportunity

Best argument for life to date is the ALH84001 meteorite.

-- microscopic analysis of structures in the meteorite found linear structures which were claimed to be fossil bacteria.

-- Most scientists in the field now agree that these are probably geological formations, not fossil life.

Possibility of Life in the Inner Solar SystemThe Mars versus our checklist:

chemical building blocks: Earth-like origin. Lots of C, N, O.

energy: reasonable sunlight. Temperature on the cold side.

liquid: Not at the present – but water ice. Strong evidence for liquid water in the distant past.

stability: currently stable but not at the best conditions

Poor chance for current life – best possibilities are at the ice caps and underground.

Reasonable chance of life in the past – depending on how long the water lasted!